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9.0 SURFACE WATER Sections 9.2 and 9.3 have not been changed 9.1 EXISTING CONDITIONS Lake Itasca is the most important surface water feature in the project area. Other areas of standing water exist but they are either temporary or are associated with wetlands. Lake Itasca has no defined inflowing or outflowing streams, therefore it can be considered a seepage lake. A generalized hydraulic gradient (Figure 24) indicates groundwater would flow into Lake Itasca from the north and leave at the south end. . , I I The topographical watershed for Lake Itasca (930 acres) is about 9 times larger than the lake surface area (see Figure 28). Although this is a fairly large watershed to lake surface ratio- (9:1), several wetland areas intercept overland flow and may act as nutrient and sediment filters to reduce nitrogen, phosphorus, and sediment inputs to the lake. In addition, the sandy soils will soak up some of the overland flow. Therefore, the lake is somewhat protected. A survey done in June 1981 indicated lake depths up to 3.3' near the center of Lake Itasca. However, a survey done in May 1986 indicates lake depths up to 8.5' (see Figure 29). For the Draft EIS modeling was done to approximate existing conditions. Based on this analysis, the predicted phosphorus concentrations in Lake Itasca were 0.03 mg-P/l. To check these calculations, a lake water sample was taken on May 28, 1986. A concentration of 0.02 mg-p/l was recorded in that sample. , - , , - I I I t -22-